The Key to His Heart
by cate78
Summary: Castle wants to show Beckett she's more than "just a cop" to him.
1. Chapter 1

**Disclaimer:** They're not mine, although I wish they were.

**A/N: **Just a small idea I had circling my brain. Not sure how good it is. Maybe cheesy and sappy and cliché? Read at your own risk. (Fair warning, I'm pretty sure my tenses are jumping all over the place.) No major spoilers really, but it's best if you're up-to-date on Season 5.

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**The Key to His Heart **

To the outside world, and indeed even to most of the people who know her, Kate Beckett is a confident, self-assured first rate detective of the NYPD; capable of intimidating and taking down the most harden of criminals. Detective Beckett is in control, deliberate and sure. Someone whom her colleagues would call the rock, the heart and soul of the team.

But that is only one facet of the extraordinary person that Richard Castle has come to know and love. Few people truly know Kate, the woman. Kate the woman, while still confident in many aspects of her life, there is also an underlying insecurity and vulnerability when it comes to her relationships.

Castle had seen glimpses of it before. Like the time they were briefly quarantined during the dirty bomb case, she had told him the fact that Josh was constantly busy gave her an excuse to keep one foot out the door just in case.

Now that they're together, Castle realizes just how deep the vulnerability seems to be. When she had burst into his loft thinking he was in trouble only to find that floozy of an entertainment reporter straddling him, the look on her face was one of disbelieve and hurt. Castle initially didn't understand why she had been so upset; surely she realizes he had no intention of sleeping with that woman and she had all but attacked him?

Then during their getaway to the Hamptons, Kate had confessed she couldn't help but wondered how many other women he had taken there before, he had tried his best to reassure her that none of the women were as important to him as her. It also made him want to kick himself thinking back to just the week prior when they were discussing Alexis' reaction upon learning of their new relationship. He had made an off-handed remark about his hundreds of girlfriends, which clearly played into her anxieties.

When he was framed for murder by 3XK and all the evidence were stacked against him, including his supposed relationship with the victim, Castle was not fool enough to think that, despite Kate reassurance to the contrary, she didn't at least for a fleeing second thought that he might've been cheating on her. But it heartened him to know that ultimately she didn't believe it.

Then the latest case they had with Leo the witness turn professional hit-man coming on the heels of their disastrous dinner with their parents. Kate had voiced her fears about their compatibility. Fearing that the bubble will eventually burst; that their inherit differences will ultimately tear them apart.

Castle knows the walls Kate had built around herself were to keep from getting hurt. If she doesn't let anybody in then there is no possibility of her losing herself and no risk of heartache. Castle also knows how lucky, how privileged he is that Kate had worked so hard to bring it down for him. For them, so that they can have a chance. He wants to show her that he will not let her down and have her build up those walls again. He wants her to know that he is in this with her for the long haul. He wants her to know that she's so much more than "just a cop" to him.

This will be their very first Christmas together and Castle wants it to be perfect. He has spent a considerable amount of brain power in the past few weeks trying to come up with a present for Kate that will convey what he feels in his heart. He had already ordered a custom-made white-gold bracelet for her. And while he knows Kate will appreciate this particular gift, ultimately she is not a superficial person that will be dazzled by fancy baubles. On the contrary, she would likely be more than a little uncomfortable and perhaps even be offended if he started showering her with expensive gifts.

To show Kate what she means to him requires something more intimate and personal. Something that will make a statement. Castle had decided to give her the keys to his loft. No, he's not asking her to move in. He knows they're nowhere close to being at that stage of their relationship. But he wants her to have the keys so that she knows she's always welcome. Into his home, into his life, into his family, into his heart.

The keys now rest in a simple metallic blue gift box attached to a Nebula-9 logo keychain. Castle had cringed slightly when he had purchase the memorabilia; it was after all, a downright cheesy show. But if it meant something to Kate, then it was important to him. He had deliberately chosen one that had a plain back so that he can add a final personal touch to it. He had taken it to an engraver to add one simple word on the back. Their word.

_Always_.

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Okay, I'd say that's the end for now. I would like to do a follow up either of Kate's reaction to the gift or maybe her gift for Castle, but frankly I'm all out of ideas right now so I can't make any promises.


	2. Kate's Gift

So the muse decided to pay me another visit. Go figure. Here we go!

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**2. Kate's Gift**

What do you get a man who has everything?

That statement is so cliché it's enough to make Kate Beckett do one of her infamous eye rolls. And yet that is exactly the dilemma she is facing. She is determined to get Castle the perfect gift for their first Christmas together but she's hard pressed to come up with something meaningful.

Being a wealthy best-selling author, as far as material things are concerned, Richard Castle already has everything he could possibly want. Not the least of which are the Ferrari, a vacation house in the Hamptons, top-of-the-line laser tag equipment and night-vision goggles. Night-vision goggles for goodness sake! What could the man possible need that for?

In some respects, Kate has already given Castle more than she's ever given any man. She has allowed him to see who she really is, flaws and all. No man before Castle has really known the full story of Kate Beckett. Through their years together Castle has learned what made her Kate. From the special place that Temptation Lane has in her memory of her mom, to the origin of the Stick-man in her precinct desk drawer to her geek-love of Nebula-9.

Castle has taken these rare glimpses and stored them away like precious treasures. And as much as their agreement was that he would watch a Nebula-9 marathon with her in exchange for her to wear her lieutenant Chloe uniform for him, Kate knew that he had agreed to watch the admittedly melodramatic and cheesy show because it meant something to her and he was willing to sit through the DVDs in order to see another layer of her.

The perfect gift for Castle is not something that any amount of money can ever buy. Kate realizes the perfect gift she can get him is another chapter in the story of herself.

While Castle is perfectly aware of Kate being a fan of his books and had teased her mercilessly during the early parts of their partnership. He never truly knew what his books and his words meant to her. She had never confessed that his books were like a life preserver; keeping her afloat during a time when she felt like she was drowning in her grieve following her mother's murder.

It is time Castle knows this truth. So Kate has decided to give him a book. His book. The one that she had stood in line for 2 hours to get him to sign. She would give him the book and tell him her story.

Kate takes the well-worn novel off her bookshelf and opens it to the page where he had signed it years ago.

_To Kate,_  
_thanks for being a fan._  
_Rick Castle_


	3. The Exchange

A/N: Okay so obviously this story has become slightly AU with the airing of "Secret Santa" but I'm just going to run with it and ignore that episode altogether. There is one exception, if you've seen the episode you'll know exactly what I'm talking about, if you haven't it'll likely just go right over your head.

I've just finished writing this and thought I'll come back to the top to add a couple of things: 1) I had no idea this chapter was going to be as long as it is when I first started out. I barely had anything in my head to write this but felt like this story just has to have this scene so I decided to just start writing. Who knew there was so much? 2) This turned out to be a somewhat bi-polar chapter. Some slightly angsty stuff along with some (hopefully) funny bits.

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**3. The Exchange**

The Christmas Alexis was 4, it was right after he had divorced Meredith, Castle had wanted to make the perfect Christmas dinner for his daughter, partly to compensate for the disappointment Alexis was feeling for not having her mommy around for the Holidays and partly to reassure himself that he can handle the responsibility of single-fatherhood. As it turned out having his own mother as a culinary mentor when he was growing up did nothing to his cooking skills.

That Christmas Eve everything that could've gone wrong went wrong. He had taken the turkey out for defrosting nowhere close to early enough and as the butterball sat in the oven still frozen to the core as dinner time ticked closer and closer he had had the brilliant idea to turn up the temperature in the hopes that it would cooked faster. Castle hadn't fare much better in his attempt at home-made mashed-potatoes, he had put way too much milk and water into the mix and it turned out to be more of a potato puree soup than mashed potatoes. Not to mentioned the fact that he had cut his own hand while slicing vegetables for another side dish. In his panicked-induced haste to somehow salvage his potatoes while trying to bandage himself up, Castle didn't notice the burning smell coming from his oven until the smoke alarm blared its warning.

In the end all that he was left with was a giant burnt out ice-ball, mashed potatoes you could drink through a straw and a very sore hand. It was a minor Christmas miracle in and of itself that the fire department had not shown up that night.

Nonetheless Castle was determined to have Christmas Eve dinner at home with his young daughter. He didn't want to be one of those sad single dads who took their kids out to a franchised restaurant getting serve an assembly line-made turkey dinner by some waiter who didn't want to be there anymore than he did. So he had looked through all the cupboards and the fridge that night to gather anything he could use to make something that was at least edible.

And that, Castle had explained to Kate when he had invited her over for Christmas Eve, was why it is a Castle family tradition to have grilled ham and cheese sandwiches, frozen fish-sticks, milk and M&M chocolates on Christmas Eve. But fear not, Castle had also quickly assured her, for Christmas Day he will demonstrate his mastery of the classic Holiday feast with all the trimmings in the ensuing years since that humbling (albeit, in hindsight, hilarious) night.

"Thanks for inviting me tonight Castle," Kate said as she wrapped herself securely around an Afghan blanket. Dinner has long since been eaten, with Kate insisting that she would clean since he had "cooked." Martha and Alexis had gone out after dinner to their respective parties. The two were now alone sitting on Castle's sofa, glasses of wine in hand, staring contentedly at the giant Christmas tree Castle had put up in the middle of his living room, fireplace crackling softly in the background.

"Thanks for coming. I wasn't sure if you would be up for it, given the less than conventional menu. Also I thought maybe you would have some traditions of your own with your dad."

"No, no. My dad typically spends the Holidays at his cabin, away from all the craziness of the city. Christmas just hasn't really been Christmas since my mom died."

Despite the fact that he writes about murders for a living, at the end of the day, he still doesn't truly know what it's really like. He can't begin to imagine how difficult it must've been that first Christmas after Johanna's murder or even all the subsequence Christmases. What he does know though is that by being there with him that night, Kate was genuinely making an effort to live her life. A life, Castle hoped, that will include him for years to come. Not only has Kate taken down her walls, she is now trying actively to destroy it, breaking down the bricks into ever smaller pieces until there is nothing left but dust. It gave him great hope that they will last. He leaned over to give her a quick kiss on the top of her head and hope it was enough to convey how he feels. They had been sitting together in companionable silence, both silently agreeing that words were not really needed.

A series of soft chimes off in the distance indicted the time. "It's midnight." Castle whispered reverently, almost as if he was afraid of disrupting the magic of the hour. "Merry Christmas Kate."

"Merry Christmas Castle," Kate answered while bringing a hand up to touch his face, drawing his head in for a soft kiss.

Castle watched as Kate got up from the couch and made her way over to the Christmas tree. She bent down to retrieve the gift she had left there earlier that evening. When Kate had arrived at his front door gift in hand, Castle immediately noted its relatively small size and his writer's imagination went into over-drive. He had peppered her with his guesses throughout the night (outside of earshot of both his mother and daughter.)

"_Is it a pair of leather hand cuffs?_" Kate had rolled her eyes.

"_Oh,_ _it's lingerie isn't it? Sexy lingerie!_"

"_Is it lace? Satin? Silk?_"

"_Negligee? Teddy? Bustier? Tell me it's a G-string._"

"_Geez Castle, I had no idea you had a thing for wearing women's underwear. I'll make a note of it for next time._" Kate had teased.

Making her way back to the couch now, Kate simply placed the package onto his lap, sat back down beside him and waited for him to open it. Castle immediately tore into the gift wrap to find a plain white cardboard box. Opening the lid he saw his own name reflected back at him. It was one of his novels; looking at the title he realized it was one of his earlier work from the Derrick Storm series. Given the somewhat battered state the book was in, Castle knew that it had been well-read. It was an odd gift to be sure and he was about to tease that it was too late for a refund if she didn't particularly enjoy the story. But one look at Kate told Castle that there was a story behind this gift.

"I stood in line for two hours for you to sign that for me." She simply said.

Castle looked stunned at her admission. Sure he had known she was a fan of his, a big fan even, one that subscribed to his website. But it never even crossed his mind that she would go to one of his book signings to get an autograph. Least of all, wait two hours for it. It was simply too un-Beckett-like. He flipped the cover over and looked down at what he had written all those years ago, not knowing that this random fan, one of hundreds of women he sign for, would one day cross his path again and make such an impact on his life. Looking back at her, Castle waited for the rest of the story because he knew there has to be a bigger story than her admitting she was a fan-girl who waited 2 hours for an autograph.

"After my mom was murdered, I was so lost. It left like everything around me was crumpling around my feet. There were days when I couldn't even get out of bed, felt like I couldn't even breathe. One day after a while, my dad and I finally made ourselves to go clear out and pack up my mom's study. That's when I found one of your books she had been reading.

I had intended to donate it to the local library. But then I started flipping through the pages and started reading. It just felt so wonderful to get transported to another world. To not have to think about all the things there were happening in real life. Then when they couldn't solve my mom's murder and it dragged on for weeks and months, I started reading more of your books. It was an escape. An escape into a world where the good guys win and the bad guys are caught and there is always justice. Even though I knew it was fiction, it still gave me hope that one day my mom will get justice of her own. It gave me strength to carry on. You saved me Castle. Even before you ever met me you saved me with your words. It made me want to have a purpose, want to get justice. Not just for my mom but for all the victims out there."

"Kate…" Castle didn't know what else to say, he was beyond overwhelmed so he simply pulled her into his embrace, tucking her head below his chin, wanting to protect her from all the bad memories and any future harm that may come to her. Castle really had no idea that his work could have such an impact on anybody, least of all Kate. Sure his novels have always been very successful, but they certainly have never been noted as great works of literature. They were simply pulp-fiction, fun easy reads. To know what they truly meant to the woman that he loves, it just takes his breath away. It also made him want to work all the more harder on his future books so that she will never be disappointed.

Then to lighten the mood a little Kate added, "So if you're still keeping score Castle, that's another plus-one for you for saving me."

"Kate," Castle tried again. "Thank you. It's perfect, I couldn't have asked for a better gift. Thank you for trusting me enough to share your story."

Castle put the novel back into cardboard box then placed the box on the table next to the couch. He got up to retrieve his gift for Kate from under the tree while making a mental note to get the book framed or somehow encased, already thinking of a prime spot of where it will go in his study.

Castle handed Kate the metal gift box, the content inside of it making a clanging sound as it shifted. Curious at the noise, Kate took the box and opened it to find the Nebula-9 logo poking out from behind a thin piece of tissue paper. She let out a bark of laughter, reached in to take the keychain out. That was when she noticed the key that was attached. Soon she realized what that key was and despite her best efforts, she couldn't quite keep the small amount of panic from bubbling up.

"It's not what you think. I'm not asking you to move in with me." Castle said immediately, knowing full well how his gift would be interpreted. Now it was his turn to tell the story.

"Kate, I love you. I meant everything that I've ever said to you. You are extraordinary, remarkable, maddening, challenging and sometimes more than a little frustrating. But I wouldn't want you to be any other way. You've inspired me so much and I'm not just talking about the books. You are so much more than a muse. You've taught me to be a better person. You've inspired me to want to be more than what I thought I was capable of. Kate, you are so much more than _just a cop_ to me. You are someone who takes care of the underdogs when nobody else would. Someone who stands up against injustices no matter the cost. Someone who is not afraid to fight against what others would consider insurmountable odds."

Castle took the keychain from Kate's hand to turn it around so that she can see the inscription on the back. "I want you to have this key because you are and always will be an integral part of my life."

As Castle finished, Kate lunged forward to kiss him passionately on the lips, one hand reaching out to dive into his hair holding him close to her. "Thank you Rick. For the key, for your patience, for your love. I love you too."

Castle's breath hitched at hearing those words from Kate for the very first time. Taking both of her hands to pull her up from the couch, he simply said "Let's go to bed."

** END **

Okay, so that was probably a little over-the-top, melodramatic and sappy but it is what it is. Hope you enjoyed it.

Merry Christmas!


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